Electrical feedthroughs for battery housings

ABSTRACT

Electrical feedthroughs for battery housings are presented. The electrical feedthroughs include a connector, a ceramic insulator, and a terminal. A first seal couples the connector to the ceramic insulator via a first braze alloy. A second seal couples the ceramic insulator to the terminal via a second braze alloy. The electrical feedthroughs can also include a spacer. A first seal couples the connector to the ceramic insulator; a second seal couples the ceramic insulator to the spacer; and the third seal couples the spacer to the terminal. The first seal, the second seal, and the third seal include, respectively, a first braze alloy, a second braze alloy, and a third braze alloy.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 62/235,083, filed Sep. 30, 2015, and entitled “ELECTRICALFEEDTHROUGHS FOR BATTERY HOUSINGS”, which is incorporated herein byreference in its entirety.

FIELD

This disclosure relates generally to electrical feedthroughs, and moreparticularly, to electrical feedthroughs for battery housings.

BACKGROUND

Thin-walled bodies are often used to house batteries owing to theirreduced weight. Such reduced weight is particularly desirable inapplications involving portable electronics. Electrical feedthroughs arecommonly incorporated into thin-walled bodies to provide access tointernal battery components. Improvements in such feedthroughs, however,are desired by the battery industry.

SUMMARY

The embodiments described herein relate to electrical feedthroughs forbattery housings. In one embodiment, the electrical feedthroughs includea ceramic insulator and a connector for coupling the ceramic insulatorto a housing. The electrical feedthroughs also include a terminaldisposed within the ceramic insulator. A first seal couples the ceramicinsulator to the connector and is formed from a first braze alloycapable of bonding the ceramic insulator and the connector. Theelectrical feedthroughs additionally include a second seal coupling theceramic insulator to the terminal. The second seal is formed from asecond braze alloy capable of bonding the ceramic insulator and theterminal.

In another embodiment, the electrical feedthroughs involve a pluralityof brazed seals. The electrical feedthroughs include a ceramic insulatorand a connector for coupling the ceramic insulator to a housing. Theelectrical feedthroughs also include a terminal disposed within theceramic insulator. A spacer is disposed between the ceramic insulatorand the terminal. The electrical feedthroughs additionally include afirst seal coupling the ceramic insulator to the connector. The firstseal is formed from a first braze alloy capable of bonding the ceramicinsulator and the connector. The electrical feedthroughs also include asecond seal coupling the ceramic insulator to the spacer. The secondseal is formed from a second braze alloy capable of bonding the ceramicinsulator and the spacer. The electrical feedthroughs further include athird seal coupling the terminal to the spacer. The third seal is formedfrom a third braze alloy capable of bonding the terminal and the spacer.

In an additional embodiment, the electrical feedthroughs involve a glassseal for electrical insulation. The electrical feedthroughs include aconnector for coupling to a housing. A terminal is disposed in theconnector and formed of a metal selected from the group consisting oftitanium, molybdenum, tungsten, and an iron-nickel-cobalt alloy. A sealglass couples the connector to the terminal pin, thereby forming theglass seal. The seal glass includes a boroaluminate glass.

Other electrical feedthroughs are presented.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be readily understood by the following detaileddescription in conjunction with the accompanying drawings, wherein likereference numerals designate like structural elements, and in which:

FIG. 1 is a cross-sectional view of an electrical feedthrough, accordingto an illustrative embodiment;

FIG. 2 is a cross-sectional view of an electrical feedthrough having aplurality of brazed seals, according to an illustrative embodiment; and

FIG. 3 is a cross-sectional view of an electrical feedthrough having aglass seal for electrical insulation, according to an illustrativeembodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to representative embodimentsillustrated in the accompanying drawings. It should be understood thatthe following descriptions are not intended to limit the embodiments toone preferred embodiment. To the contrary, it is intended to coveralternatives, modifications, and equivalents as can be included withinthe spirit and scope of the described embodiments as defined by theappended claims.

Referring to FIG. 1, a cross-sectional view is presented of anelectrical feedthrough 100, according to an illustrative embodiment. Theelectrical feedthrough 100 includes a ceramic insulator 102 that may becrystalline, amorphous, or a combination thereof. Non-limiting examplesof the ceramic insulator 102 include an aluminum oxide material, (e.g.,Al₂O₃), a silicon oxide material (e.g., SiO₂), an aluminum silicon oxidematerial (e.g., 3Al₂O₃.2SiO₂), a silicon nitride material (e.g., Si₃N₄),a titanium oxide material (e.g., TiO₂), and a zirconium oxide material(e.g., ZrO₂). Other materials for the ceramic insulator 102 arepossible. In some embodiments, the ceramic insulator 102 includes analuminum oxide material. In some embodiments, the ceramic insulatorexhibits a resistivity greater than 10⁹ Ω-cm. In some embodiments, suchas that shown in FIG. 1, the ceramic insulator 102 is formed as asleeve.

The electrical feedthrough 100 also includes a connector 104 forcoupling the ceramic insulator 102 to a housing 106. In someembodiments, the connector 104 can be shaped to mate with an orificethat traverses the housing 106. Such mating may be assisted by bonding(e.g., soldering, brazing, welding, epoxying, etc.) that hermeticallyseals the connector 104 to the housing 106. The connector 104 may allowthe ceramic insulator 102 to be disposed therein (e.g., formed as aferrule). In some embodiments, the connector 104 is formed of astainless steel. In further embodiments, the stainless steel is selectedfrom the group consisting of stainless steel 304, stainless steel 316, astainless steel 316L, or other 300 series stainless steel. In otherembodiments, the connector may be formed of an aluminum. In someembodiments, the connector 104 is coupled to the housing 106.

FIG. 1 depicts the housing 106 as a shell, although this depiction isnot intended as limiting. In embodiments where the housing 106 is ashell, the shell may be a stainless steel shell. In further embodiments,the housing 106 contains a battery therein.

A first seal 108 couples the ceramic insulator 102 to the connector 104.The first seal includes a first braze alloy capable of bonding theceramic insulator 102 to the connector 104. This coupling may involve ahermetic seal between the ceramic insulator 102 to the connector 104. Insome embodiments, the first braze alloy is selected from the groupconsisting of silver alloys and gold alloys. In further embodiments, thefirst braze alloy incorporates alloying elements that, in total, do notexceed 50 weight percent. For example, and without limitation, the firstalloy may be Ag₇₂Cu₂₈ (i.e., silver alloys). In another non-limitingexample, the first alloy may be Au₈₀Sn₂₀ (i.e., gold alloys). Moreover,the silver alloys and the gold alloys are not restricted to alloyingelements of, respectively, Cu and Sn. Other alloying elements arepossible, including combinations thereof. The alloying elements mayenhance a wettability of the first braze alloy to the ceramic insulator102, the connector 104, or both, during brazing (i.e., during formationof the first seal 108).

The electrical feedthrough 100 also includes a terminal 110 disposed inceramic insulator 102 via a sleeve hole 114. In FIG. 1, the terminal 110is depicted as a cylindrically-symmetric pin. However, this depiction isfor purposes of illustration only. Other shapes are possible for theterminal 110. In some embodiments, the terminal 110 includes aluminum,which may be a pure metal or an alloy (e.g., aluminum 1100). Theterminal 110 is shaped to allow coupling to the ceramic insulator 102via brazing. By incorporating aluminum, the terminal 110 may exhibit aductility that can accommodate differentials in thermal expansion duringbrazing (i.e., differentials in thermal expansion between the terminal110 and the ceramic insulator 102). In other embodiments, the terminalis formed of a stainless steel. In further embodiments, the stainlesssteel is selected from the group consisting of stainless steel 304,stainless steel 316, a stainless steel 316L, or other 300 seriesstainless steel. In some embodiments where the connector 104 is coupledto the housing 106 and a battery is contained in the housing 106, theterminal 110 may be electrically connected to the battery.

A second seal 112 couples the ceramic insulator 102 to the terminal 110.This coupling may seal the ceramic insulator 102 to the terminal 110hermetically. The second seal 112 is formed from a second braze alloycapable of bonding the ceramic insulator 102 and the terminal 110. Thesecond braze alloy may be selected from the group consisting of analuminum alloy and a gold alloy. For instances where the second brazealloy is the aluminum alloy, the second braze alloy may incorporatealloying elements that may, in total, range between 5-50 weight percentof the aluminum alloy (e.g., Al₈₈Si₁₂). However, other ranges arepossible. Non-limiting examples of alloying elements for the aluminumalloy include silicon and germanium. For instances where the secondbraze alloy is the gold alloy, the second braze alloy may incorporatealloying elements that, in total, do not exceed 50 weight percent. Forexample, and without limitation, the second alloy may be a gold-tinalloy with tin accounting for less than 50 weight percent (e.g.,Au₈₀Sn₂₀). Other alloying elements, however, are possible for the goldalloy.

With further reference to FIG. 1, in various embodiments, both secondseal 112 and terminal 110 can be formed of alloys having similar bondingtemperatures. Without wishing to be limited to a particular theory ormode of action, similar bonding temperatures in second seal 112 andterminal 110 can facilitate bonding of second seal 112 to terminal 110.For example, the bonding temperatures of second seal 112 and terminal110 can be within 10° C., 20° C., 30° C., 40° C., or 50° C. of eachother. Similar bonding temperatures can be found where alloys have thesame or similar alloy composition.

In some aspects, both second seal 112 and terminal 110 can be formed ofan alloy with the same primary metal component (e.g., aluminum orsilver). For example, second seal 112 can both be formed of aluminumalloys. In various additional aspects, second seal 112 can be formed ofthe same alloy composition as terminal 110. For example, second seal 112and terminal 110 can both be formed of the same aluminum alloy.

Likewise, first seal 108 and connector 104 can be made of alloys withsimilar bonding temperatures. In some variations, first seal 108 andconnector 104 can be made of alloys with the same primary metalcomponent (e.g., aluminum or silver). In some instances, first seal 108and connector 104 can be made of the same alloy (e.g., the same aluminumalloy).

In FIG. 1, the electrical feedthrough 100 is depicted as having theconnector 104, the ceramic insulator 102, and the terminal 110 in anested configuration. However, this depiction is not intended aslimiting. Other configurations are possible.

In some embodiments, a nickel layer may coat the connector 104, theterminal 110, or both. This coating may be in whole or in part. Infurther embodiments, a gold layer is disposed on the nickel layer. Thegold layer may be disposed over the entire nickel layer or portionsthereof.

It will be appreciated that the electrical feedthrough 100 may utilize afirst configuration where the connector 104 includes the stainless steeland the terminal 110 includes aluminum or a second configuration wherethe connector 104 includes aluminum and the terminal 110 includes thestainless steel. In the second configuration, the first seal 108 isformed from the second braze alloy and the second seal 112 is formedfrom the first braze alloy. Thus, a configuration of materials in theelectrical feedthrough 100 is reversible. In FIG. 1, the electricalfeedthrough 100 corresponds to the first configuration and theassociated disclosure relates to this configuration.

In operation, a first surface of the terminal 110 and a second surfaceopposite the first surface of the terminal 110 are electrically coupledto, respectively, a current source and a current sink, or vice versa. Avoltage gradient between the current source and the current sink induceselectrical current to flow through the terminal 110. The terminal 110 iscoupled to the connector 104 via the ceramic insulator 102, the firstseal 108, and the second seal 112. However, despite this coupling, theceramic insulator 102 electrically isolates the terminal 110 from theconnector 104. Electrical current is therefore constrained to flowthrough the terminal 110, which is electrically-conductive. It will beappreciated that the connector 104 can be configured to allowincorporation of the electrical feedthrough 100 into thin-walled bodiesor shells, such as that depicted in FIG. 1. Such thin-walled bodies orshells may be applicable to batteries where low weight is desired. Athin-walled body means that the ratio of the body's thickness to thediameter of the orifice that traverses the housing 106 is 1:10 or less.

Referring now to FIG. 2, a cross-sectional view is presented of anelectrical feedthrough 200 having a plurality of brazed seals, accordingto an illustrative embodiment. The electrical feedthrough 200 includes aceramic insulator 202 that may be crystalline, amorphous, or acombination thereof. Non-limiting examples of the ceramic insulator 202include an aluminum oxide material, (e.g., Al₂O₃), a silicon oxidematerial (e.g., SiO₂), an aluminum silicon oxide material (e.g.,3Al₂O₃.2SiO₂), a silicon nitride material (e.g., Si₃N₄), a titaniumoxide material (e.g., TiO₂), and a zirconium oxide material (e.g.,ZrO₂). Other materials for the ceramic insulator 202 are possible. Insome embodiments, the ceramic insulator 202 includes an aluminum oxidematerial. In some embodiments, the ceramic insulator exhibits aresistivity greater than 10⁹ Ω-cm. In some embodiments, such as thatshown in FIG. 2, the ceramic insulator 202 is formed as a sleeve.

The electrical feedthrough 200 also includes a connector 204 forcoupling the ceramic insulator 202 to a housing 206. The connector 204,which may be formed of an iron-nickel-cobalt alloy (e.g., Kovar), isshaped to mate with an orifice that traverses the housing 206. Suchmating may be assisted by bonding (e.g., soldering, brazing, welding,epoxying, etc.) that hermetically seals the insulator 202 to the bodywall. The connector 204 may allow the ceramic insulator 202 to bedisposed therein (e.g., formed as a ferrule). In some embodiments, theconnector 204 is coupled to the housing 206. FIG. 2 depicts the housing206 as a shell, although this depiction is not intended as limiting. Inembodiments where the housing 206 is a shell, the shell may be astainless steel shell. In other embodiments, the housing 206 may be analuminum shell. In further embodiments, the housing 206 contains abattery therein.

The electrical feedthrough 200 additionally includes a terminal 208disposed within the ceramic insulator 202. In FIG. 2, the terminal 208is depicted as a cylindrically-symmetric pin. However, this depiction isfor purposes of illustration only. Other shapes are possible for theterminal 208. In some embodiments, the terminal 208 includes aluminum,which may be a pure metal or an alloy (e.g., aluminum 1100). In theseembodiments, by incorporating aluminum, the terminal 208 may exhibit aductility that can accommodate differentials in thermal expansion duringbrazing. In embodiments where the connector 204 is coupled to thehousing 206 and the housing 206 contains the battery therein, theterminal 208 may be electrically-coupled to a cathode of the battery.

The electrical feedthrough 200 also includes a spacer 210 disposedbetween the ceramic insulator 202 and the terminal 208. The terminal 208traverses the spacer 210, or a portion thereof, to become disposedwithin the ceramic insulator 202. The spacer 210 may have a spacer holetherethrough. The spacer 210 serves to enable a joint that spans theceramic insulator 202 and the terminal 208. In some embodiments, thespacer 210 is formed of an iron-cobalt-nickel alloy (e.g., Kovar). Infurther embodiments, the connector 204 is coupled to the housing 206 andthe housing 206 contains the battery therein. In these embodiments, theterminal 208 is electrically-coupled to the cathode of the battery

A first seal 212 couples the ceramic insulator 202 to the connector 204and is formed from a first braze alloy capable of bonding the ceramicinsulator 202 and the connector 204. This coupling may involve ahermetic seal between the ceramic insulator 202 to the connector 204.Similarly, a second seal 214 couples the ceramic insulator 202 to thespacer 210 and is formed from a second braze alloy capable of bondingthe ceramic insulator 202 and the spacer 210. The second seal 214 mayhermetically couple the ceramic insulator 202 to the spacer 210.Moreover, a third seal 216 couples the terminal 208 to the spacer 210and is formed from a third braze alloy capable of bonding the terminal208 and the spacer 210. Such coupling may seal the terminal 208 to thespacer 210 hermetically. It will be appreciated that the spacer 210 actsas a transition piece between the terminal 208 and the insulator 202. Inthis capacity, the spacer 210 may accommodate differences in thermalexpansion during brazing by offering an intermediate thermal expansionbetween the ceramic insulator 202 and the terminal 208 (e.g., to preventcracks, tearing, etc.).

In some embodiments, the first braze alloy, the second braze alloy, andthe third braze alloy include a gold alloy. In these embodiments, thegold alloy incorporates alloying elements that, in total, do not exceed50 weight percent. For example, and without limitation, the gold alloymay incorporate tin in an amount less than 50 weight percent (e.g.,Au₈₀Sn₂₀). However, other alloying elements are possible, includingcombinations thereof. The alloying elements of the gold alloy mayenhance, during brazing, a wettability of the gold alloy to theinsulator 202, the connector 204, the spacer 210, the terminal 208, orcombinations thereof. It will be understood that the first braze alloy,the second braze alloy, and the third braze alloy are not restricted toa common composition of the gold alloy. In further embodiments, thespacer 210 is formed of an iron-cobalt-nickel alloy (e.g., Kovar).

In some embodiments, a nickel layer may coat the connector 204, theterminal 208, the spacer 210, or combinations thereof. This coating maybe in whole or in part. In further embodiments, a gold layer is disposedover the nickel layer. The gold layer may be disposed over the entirenickel layer or portions thereof.

In operation, a first surface of the terminal 208 and a second surfaceopposite the first surface of the terminal 208 are electrically coupledto, respectively, a current source and a current sink, or vice versa. Avoltage gradient between the current source and the current sink induceselectrical current to flow through the terminal 208. The terminal 208 iscoupled to the connector 204 via the spacer 210, the ceramic insulator202, the first seal 212, the second seal 214, and the third seal 216.However, despite this coupling, the ceramic insulator 202 electricallyisolates the terminal 208 from the connector 204. Electrical current istherefore constrained to flow through the terminal 208, which iselectrically conductive. It will be appreciated that the connector 204can be configured to allow incorporation of the electrical feedthrough200 into thin-walled bodies or shells, such as that depicted in FIG. 2.Such thin-walled bodies or shells may be applicable to batteries wherelow weight is desired.

Now referring to FIG. 3, a cross-sectional view is presented of anelectrical feedthrough 300 having a glass seal 302 for electricalinsulation, according to an illustrative embodiment. The electricalfeedthrough 300 includes a connector 304 for coupling to a housing 306.The connector 304 is shaped to mate with an orifice that traverses thehousing 306. Such mating may be assisted by bonding (e.g., soldering,brazing, welding, epoxying, etc.) that hermetically seals the connector304 to the housing 306. The connector 304 may include throughhole (e.g.,formed as a ferrule) although other geometries are possible. In someembodiments, the connector 304 is formed of a stainless steel. Infurther embodiments, the stainless steel is selected from the groupconsisting of stainless steel 304, stainless steel 316, and stainlesssteel 316L. In some embodiments, the connector 304 is coupled to thehousing 306. FIG. 3 depicts the housing 306 as a shell, although thisdepiction is not intended as limiting. In embodiments where the housing306 is a shell, the shell may be a stainless steel shell. In furtherembodiments, the housing 306 contains a battery therein.

The electrical feedthrough 300 also includes a terminal 308 disposed inthe connector 304 and formed of a metal selected from the groupconsisting of titanium, molybdenum, tungsten, and an iron-nickel-cobaltalloy (e.g., Kovar). The terminal 308 is shaped to allow coupling to theconnector 304 via the glass seal 302. In embodiments where the connector304 is coupled to the housing 306 and the housing 306 contains thebattery therein, the terminal 308 may be electrically-coupled to acathode of the battery.

The electrical feedthrough 300 additionally includes a seal 310 couplingthe connector 304 to the terminal 308. The seal 310 bridges a gapbetween the connector 304 and the terminal pin 308 to form the glassseal 302, which may be a hermetic seal. The seal 310 includes aboroaluminate glass that incorporates a boron oxide material (e.g.,B₂O₃) and an aluminum oxide material (e.g., Al₂O₃). For example, andwithout limitation, the boroaluminate glass may contain 35-45 weightpercent of boron oxide and 25-35 weight percent of aluminum oxide. Inanother non-limiting embodiment, the boroaluminate glass may contain30-50 weight percent of boron oxide and 10-25 weight percent of aluminumoxide. Other weight percents for the boroaluminate glass are possible.The boroaluminate glass also incorporates complementary oxide materials,whether individually or in combination, such that a total weight percentsums to 100 weight percent. Such complementary oxide materials includemagnesium oxide, calcium oxide, strontium oxide, barium oxide, titaniumoxide, zirconium oxide, molybdenum oxide, tungsten oxide, iron oxide,nickel oxide, and cobalt oxide. Other oxide materials are possible. Ingeneral, the boroaluminate glass is an amorphous insulator and mayexhibit a resistivity greater than 10⁹ Ω-cm. In some embodiments, theboroaluminate glass includes barium oxide. In such embodiments, theboroaluminate glass may be a BaBAl-1 glass. In some embodiments, theboroaluminate glass includes calcium oxide. In these embodiments, theboroaluminate glass may be a CaBAl-12 glass.

In operation, a first surface of the terminal 308 and a second surfaceopposite the first surface of the terminal 308 are electrically coupledto, respectively, a current source and a current sink, or vice versa. Avoltage gradient between the current source and the current sink induceselectrical current to flow through the terminal 308. Such electricalcurrent flows along the voltage gradient from higher voltage to lowervoltage. The terminal pin 308 is coupled to the connector 304 via theglass seal 302. However, despite this coupling, the glass sea; 302,being an amorphous insulator, electrically isolates the terminal 308from the connector 304. Electrical current is therefore constrained toflow through the terminal 308, which is electrically conductive. It willbe appreciated that the connector 304 can be configured to allowincorporation of the electrical feedthrough 300 into thin-walled bodiesor shells, such as that depicted in FIG. 3. Such thin-walled bodies orshells may be applicable to batteries where low weight is desired.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of the specificembodiments described herein are presented for purposes of illustrationand description. They are not target to be exhaustive or to limit theembodiments to the precise forms disclosed. It will be apparent to oneof ordinary skill in the art that many modifications and variations arepossible in view of the above teachings.

What is claimed is:
 1. An electrical feedthrough, comprising: a ceramic insulator; a connector for coupling the ceramic insulator to a housing; wherein the connector comprises a cylindrical body with a central opening for receiving the ceramic insulator, the connector further comprising a lip surrounding the cylindrical body, the lip comprising an inner surface for bonding to the housing; wherein the housing has a thickness that is less than a thickness of the connector; a terminal disposed within the ceramic insulator; a first seal coupling the ceramic insulator to the connector, the first seal formed of a first braze alloy capable of bonding the ceramic insulator and the connector; and a second seal coupling the ceramic insulator to the terminal, the second seal formed of a second braze alloy capable of bonding the ceramic insulator and the terminal.
 2. The electrical feedthrough of claim 1, wherein the terminal comprises a material selected from stainless steel and aluminum.
 3. The electrical feedthrough of claim 2, wherein the terminal comprises aluminum.
 4. The electrical feedthrough of claim 1, wherein the connector comprises a material selected from stainless steel and aluminum.
 5. The electrical feedthrough of claim 1, wherein the first braze alloy is selected from a silver alloy and a gold alloy.
 6. The electrical feedthrough of claim 1, wherein the second braze alloy is selected from the group consisting of an aluminum alloy and a gold alloy.
 7. The electrical feedthrough of claim 3, wherein the second braze alloy is an aluminum alloy. 